Bogie Region Research Articles

Numerical approach for the simulation of flow-induced noise around a structure with complex geometry: High-speed train bogie in a cavity

The bogie region is a significant source of aerodynamic noise on high-speed trains. Owing to its complex geometry and flow field, numerical simulations using computational fluid dynamics are especially challenging. The main challenge is to achieve a grid with adequate resolution, especially in the boundary layer, while ensuring computational affordability. This challenge is addressed here by employing a hybrid grid, integrating a structured hexahedral mesh near solid surfaces with an unstructured polyhedral mesh in the remaining volume. To limit the number of cells in the boundary layer region, the delayed detached eddy simulation method is adopted. Additionally, to achieve a further reduction in the cell count, the Reynolds number of the model is decreased by scaling down the model size and lowering the inflow speed. The hybrid grid generation and numerical settings are guided by validated simulations of flow over cylinders. A grid sensitivity study, conducted with a simplified half-width bogie model, reveals the meshing requirements for the full-width model. Aerodynamic results highlight the rear section of the cavity and bogie as primary noise sources, emphasizing the critical role of the detached shear layer from upstream components. Time-resolved surface pressure data are input into the Ffowcs Williams–Hawkings equation for far-field noise calculation. The results indicate that the sound energy is concentrated below 200 Hz in the full-scale model, with the cavity contributing more than the bogie. This study provides a practical numerical approach for simulating a structure with complex geometry, offering insights for realistic model simulations.

Numerical Investigation on Aerodynamic Noise Source Identification and Far-Field Noise Characteristics of the High-Speed Train Bogie Region

Numerical Investigation on Aerodynamic Noise Source Identification and Far-Field Noise Characteristics of the High-Speed Train Bogie Region

Effect of geometry simplification and boundary condition specification on flow field and aerodynamic noise in the train head and bogie region of high-speed trains

Effect of geometry simplification and boundary condition specification on flow field and aerodynamic noise in the train head and bogie region of high-speed trains

Influence of the contraction section configuration and deflector layout density on the wind-snow flow characteristics inside the ice snow wind tunnel for railway vehicles

The significant accumulation of snow and ice in the bogie region severely compromises operational quality and poses a safety hazard to high-speed trains. To enhance testing capabilities for assessing ice and snow accumulation within bogie regions, this study conducts numerical investigations into the influence of contraction section configuration and deflector layout density on wind-snow flow quality within an ice and snow wind tunnel. The predictive accuracy of the numerical method is comprehensively validated against wind-snow wind tunnel tests, involving a comparison of airflow velocity in the test section and snow accumulation thickness on the channel's floor. The results demonstrate that the coupled numerical method of Improved Delayed Detached Eddy Simulation (IDDES) and Discrete Phase Model (DPM) is a reliable tool for analyzing wind-snow flow characteristics within an ice and snow wind tunnel. Furthermore, compared to the vickers curve and bicubic curve, quintic curves applied to the contraction section consistently compress and accelerate airflow. This contributes to a more uniform flow characterized by lower stream-wise fluctuation levels, pitch angles, and yaw angles in the test section, thereby significantly enhancing the overall flow quality of wind and snow. Thus, the quintic curves or smoother curves are recommended for the design of the contraction section in ice and snow wind tunnels. Moreover, increasing the deflector number leads to a noticeable improvement in flow quality inside the test section, while resulting in increased snow accretion on the windward surfaces of deflectors. Hence, a medium-level deflector density is suggested for designing ice and snow wind tunnels to achieve a better balance between flow quality and the additional snow accretion inside the channel.

Research on snow prevention in the bogie region based on active blowing method

To reduce excessive snow accumulation on bogie surfaces during high-speed train operations in cold regions, two active blowing schemes are designed in this study based on the shape of the bogie cavity and the relative position of the brake caliper. The unsteady Reynolds-averaged Navier–Stokes algorithm coupled with a discrete phase model was used to calculate the airflow and snow flow under the train. Moreover, the algorithm is employed to explore the impact of active blowing on the flow field characteristics and snow accumulation in the bogie region. Results show that active blowing changes the upward airflow in the bogie region, causing air at the bottom of the train to flow outwards, carrying off numerous snow particles from the bogie region. Active blowing accelerates the surface friction velocity on the bogie, increases the shear force on snow particles, and effectively reduces the snow accumulation on the bogie surface. The foregoing observation indicates that active blowing has considerable potential for snow accumulation prevention.

Analysis of Snow Distribution and Displacement in the Bogie Region of a High-Speed Train

Analysis of Snow Distribution and Displacement in the Bogie Region of a High-Speed Train

Numerical Investigation of Snow Prevention in the Bogie Region of High-Speed Trains with Active Blowing under Crosswind Conditions

Numerical Investigation of Snow Prevention in the Bogie Region of High-Speed Trains with Active Blowing under Crosswind Conditions

Numerical Simulations of Snow Accumulation in the Bogie Region of a Train Considering Snow Particle Rotation

Numerical Simulations of Snow Accumulation in the Bogie Region of a Train Considering Snow Particle Rotation

Effect of Bogie Cavity End Wall Inclination on Flow Field and Aerodynamic Noise in the Bogie Region of High-Speed Trains

Effect of Bogie Cavity End Wall Inclination on Flow Field and Aerodynamic Noise in the Bogie Region of High-Speed Trains

Aerodynamic noise from a high-speed train bogie with complex geometry under a leading car

Among the various aerodynamic noise sources associated with high-speed trains, the bogie regions, and particularly the leading bogie, contribute most to the overall noise. To control this noise, insight into the noise generation mechanisms is imperative but relevant studies are limited due to the difficulties of simulating the flow in regions with complex geometry. An investigation is presented of the aerodynamic noise from a bogie under the leading car of a high-speed train using Delayed Detached Eddy Simulation method. A hybrid grid system is utilized to simulate the flow field, which provides input for the far-field noise calculations based on the Ffowcs Williams and Hawkings equation. Analysis shows that the outer bogie components experience large pressure fluctuations as they are immersed in the shear layer detached from upstream, which is therefore identified as playing a critical role in the noise generation. The resulting noise spectra are broadband and dominated by low frequencies. Compared with the bogie, the bogie cavity and train nose emit 5 dB greater sound power for the current geometry. This study improves understanding of the mechanisms behind the generation of aerodynamic noise in train bogies and lays the foundations for future studies of train bogie noise reduction.

Anechoic wind tunnel noise tests for high-speed train bogie aerodynamic noise characterization

At speeds normally reached by high-speed trains (above 300 km/h), aerodynamic noise becomes significant. The bogie region is one of the main sources of aerodynamic noise in high-speed trains due to incoming flow impinging the bogie components and the cavity steps. Noise tests were performed in the Railway Technical Research Institute's anechoic wind tunnel placed in Tokyo, Japan, for different flow speeds from 100 km/h up to 250 km/h using simple shapes representing bogie components, and a 1:5 scale simplified bogie installed in a cavity. The noise spectra radiated by the simple shapes placed at different heights relative to the upstream cavity step are presented, showing the relation between the component geometry and position in the cavity with the produced noise. In addition, the measured noise spectra are shown for different configurations of the 1:5 scale simplified bogie: bare, only with front motor and gearbox, only with rear motor and gearbox and with all of them. The presented results aim to provide a better understanding of how the aerodynamic noise is produced in the bogie region of a high-speed train, and to be used for the prediction models adjustment or validation.

Flow control for aerodynamic drag reduction of a high-speed train with diversion slots on bogie regions

A diversion slot is one of the potential mechanical devices to reduce high-speed train underbody aerodynamic resistance. This research aims to investigate the effectiveness of using diversion slots as a means of passive flow control to reduce the resistance of a high-speed train. Two different diversion slot designs, i.e., the big diversion slot (Bds) and the small diversion slot (Sds), placed at two installation locations near the bogie cabin end walls in six configurations are used. The results indicate that drag of the tail car is significantly reduced by 7.8%, 5.5%, 9.0%, and 9.4% using the configurations in cases 2 and 4–6, while an increase in 0.4% is experienced in case 3. Consequently, the total train aerodynamic resistance reduces by 1.9%, 0.2%, 3.0%, 4.2%, and 0.4% in cases 2–6, respectively, as compared to case 1. By evaluating the flow structure, we found that the diversion slots trigger flow separation, deflecting the airflow from entering the bogie regions, increasing flow turbulence and reducing the flow velocity. It efficiently improves the wake flow structure by reducing the wake strength, thereby increasing the tail nose surface pressure, thus reducing the tail car's aerodynamic drag. This study proposes a novel approach for reducing aerodynamic drag in high-speed trains, improving the underbody flow and wake characteristics.

Numerical Research of the Snow and Ice Accumulation in the Bogie Region of High-speed Train

Numerical Research of the Snow and Ice Accumulation in the Bogie Region of High-speed Train

Numerical study on slipstream-induced snow drifting and accumulation in the bogie region of a high-speed train passing the snowy ballast bed

When a high-speed train (HST) passes the snowy ballast bed in winter, the slipstream can induce snow drifting and generate snow accumulation problem in the bogie region. The conventional numerical method has utilized the way that snow particles drift with the incoming flow around a stationary train with moving ground (STMG). In this paper, the sliding mesh technique is applied to reproduce the actual scene of a moving train with stationary ground (MTSG). Coupled with the discrete phase model, a novel simulation method for snow accumulation is presented. The comparisons between the STMG and MTSG are conducted, including the flow field, snow distribution and accumulation features. The results show that similar flow field around the HST is captured by the two methods. The MTSG predicts more dispersed snow distribution in the Bogie 2 region than the STMG. The total mass of accumulated snow on bogies and cavities obtained by MTSG is 18.31% more than that derived from STMG. The presented method achieves the relative motion among the HST-snow-ground and the sweeping process of the slipstream on the snow surface is fully considered. In engineering applications, it provides a feasible method to explore the snow accumulation phenomenon of HSTs in more scenes, such as the intersecting of two HSTs.

Numerical Investigation on the Flow underneath a High-Speed Train of Six Coaches Marshalled with Different Bogies

The turbulent flow developed underneath a scaled high-speed train of six coaches featured with both conventional and articulated bogies is investigated based on computational fluid dynamics to establish a contribution to train aerodynamics. The numerical simulations are verified against the experimental measurements. It is found that strong unsteady flow develops around the train, particularly at the regions of nose car, leading bogie, articulated bogies, inter-carriage gaps and tail car, due to flow separations and vortex interactions generated around the geometries. High intensity turbulence appears around the nose, bogies, inter-carriage gaps and tail. Strong vortices and high degree of unsteadiness are produced within the flow between the train underbody and the ground, making the flow developed around the bogie regions of high turbulence. Interaction from the inter-car gap leads to a particularly strong vortical flow around the articulated bogie, causing a large slipstream in the regions close to the airspring and a larger drag. Thus the bogie configuration has a noticeable influence on the train underbody flow.

Research on movement and deposition of snow particles with different shapes in the bogie region

Natural snow particles come in various complex shapes and have different forces acting on them. The forces acting on snow particles of various shapes are customised in this study based on the shape correction coefficients and sphericity theories. The wind and snow flow at the bottom of the train are solved by coupling the unsteady Reynolds-averaged Navier–Stokes simulation with the discrete phase model to explore the snow accumulation problem of high-speed train bogies more realistically. The findings reveal that changing the morphology of snow particles impacts their resistance to movement in the bogie region, affecting their mobility in the bogie region. Snow particles with higher resistance will stay in the low-speed zone of the bogie region, increasing snow particle concentration and accumulation, whereas snow particles with lower resistance follow airflow movement and gather fewer in the low-speed zone. Different shapes of snow particles accumulate in different amounts on the bogie components, with the most accumulation by spherical snow particles in the braking system and suspension system surface. Therefore, using spherical snow particles to simulate wind and snow flow phenomenon at the bottom of the train can indicate the worst case.

Evaluating railway noise sources using distributed microphone array and graph neural networks

Identifying and evaluating railway noise sources is beneficial for establishing more targeted suppression and mitigation strategies. This paper proposes a novel approach to evaluate dominant railway noise sources for all bogie regions, by using an array of microphones and a physics-informed graph neural networks (GNN) model. The GNN model encodes not only the acoustic data collected by the microphone array but also the spatial relationship between noise sources and microphones, and it also considers the physical background of sound in terms of Doppler effect and acoustic attenuation . In-situ measurements of railway noises have been taken on an operating metro line to train and validate the GNN model which exhibits satisfactory performance in evaluating the noise sources of interest. The proposed approach enables a more flexible and cost-effective microphone array implementation strategy in comparison to the commonly adopted commercialized acoustic beamforming system.

Investigation on aerodynamic noise generated from the simplified high-speed train leading cars

The aerodynamic noise behavior of flow passing the simplified leading car and nose car scale models of a high-speed train is investigated through the vortex sound theory and acoustic analogy approach. The unsteady flow developed around the geometries is solved numerically and the data are applied to study the near-field quadrupole sound source and calculate the far-field noise radiated. It is found that the turbulent flow developed around the leading car is characterized by multi-scale vortices separated from the geometries. The intensity of volume dipole source is much larger than that of volume quadrupole source and the volume dipole source becomes the predominate source of the near-field quadrupole noise. The flow is separated noticeably in the regions of the nose, bogies, bogie cavities, and train tail of the leading car where the pressure fluctuations are generated largely upon the solid surfaces and correspondingly a dipole noise of high level is produced. By comparison, the noise contribution from the leading bogie and bogie cavity is larger than that from the other components. Moreover, the numerical and experimental results of train nose car model demonstrate that the flow around the bogie region is the dominant aerodynamic sound source. Therefore, the flow-induced noise generated from the leading cars may be reduced efficiently within a certain frequency range and specific direction by mitigating the flow interactions around the areas of leading bogie and bogie cavity.

Effect of simplifying bogie regions on aerodynamic performance of high-speed train

Effect of simplifying bogie regions on aerodynamic performance of high-speed train

Investigation of ice and snow accumulations on the bogie areas of high-speed trains using ice wind tunnel experiments

Accumulated snow and ice will severely influence the safe operation of high-speed trains in snowy weather, where the snow and ice in the bogie region are the main concerned problems that contribute to such issues. The work presented in this paper initiated experimental studied snow and ice accumulation on the running bogies of the high-speed trains to clarify the snow and ice accumulation process and causes. Two original and two optimized cases with protective schemes combined with electoral heating and an air-flow deflector under the customized train body were adopted to carry out the snow and ice wind tunnel experiments in the Icing-snowing Wind Tunnel (ISWT) of Central South University (CSU). The distributions and mass of the snow and ice were analysed, and the preliminary conclusions were drawn: the leeward side and the depressions of the bogies accumulated a layer of snow, and the melt water sprayed by the rotating brake discs flew everywhere, which contributed to rapidly growing icicles on the bogies and train body during the experiments. Deflectors, protective sleeves and different kinds of heating methods were adopted according to the original cases to optimized where they should be placed, they were capable of reducing the snow and ice mass by 62.9% and 50.4% from the original trailer and motor bogie, respectively. Thus, the optimized schemes were confirmed to be effective to show great application potential to reduce mass and increase running safety for high-speed trains in winter in cold regions.